The present invention relates to an apparatus for recording a color image by use of a latent electrostatic image, and particularly relates to a color recording apparatus in which toner images obtained by repeating the processes of charging, latent image formation and development are en bloc transferred onto a recording sheet.
There is known a conventional color recording apparatus as disclosed in Japanese Unexamined Patent Publication No. Sho. 58-116553. In this apparatus, two-color toner images are first formed on a photoreceptor by performing two-times the processes of charging, image-portion exposure and reversal development, and then the resultant toner images are en bloc transferred onto a recording sheet. In addition, the second charging is performed by use of a scorotron after the first development to make the potential of image portions approximately equal to that of non-image portions, and a soft-type one-component magnetic toner is used for the second development, to prevent electrical scraping of the first toner and to prevent the second toner from adhering to first image portions (the latter phenomenon is hereinafter referred to as "color contamination").
However, in the method disclosed in Japanese Unexamined Patent publication No. Sho. 58-116553, since lines of electric force develop near the photoreceptor and between the first image portions and non-image portions at the time of the second charging, peripheral portions of the first image are not charged enough and the electric potential of those portions remains low. As a result, the peripheral portions of the first image are also developed in the second development, causing the quality of the first image to deteriorate. FIG. 6 schematically shows the occurrence of the development of the peripheral portions of the first image.
Further, the method is also accompanied by the following problem. Since a development bias needs to be set so as to avoid the color contamination in the second development, the difference between the second development bias and the potential of the first image portions becomes large. As a result, the first toner may be scraped electrically and mixed into a second developer, so that the density of the first image is decreased and the life of a second developing agent is reduced.